Microelectromechanical systems (MEMS) are integrated micro devices or systems combining electrical and mechanical components. Some MEMS devices may be fabricated using standard integrated circuit batch processing techniques and have a variety of applications including sensing controlling and actuating on a micro scale. MEMS devices may function individually or in arrays to generate effects on a macro scale.
Certain MEMS devices require a vacuum environment in order to obtain maximum performance. The vacuum package also provides protection in an optimal operating environment for the MEMS device. Examples of these MEMS devices are infrared MEMS such as bolometers. In addition to the necessity of a vacuum or otherwise controlled environment for an infrared bolometer, infrared MEMS devices may require an optically-transparent cover, or lid structure. These device wafer lids are often coated with an anti-reflective coating to reduce the reflective properties and increase the optical transmission properties of the device wafer lid. Typically, the anti-reflective coating is patterned with a liftoff method that requires a thick photoresist, which is hard to remove after the anti-reflective coating is deposited on the device wafer lid. This is due primarily to the extremely high temperatures at which the anti-reflective coating must be deposited on the device wafer lid.